Chemistry SM-1131Week 2 Lesson 2

Dr. Jesse ReichAssistant Professor of Chemistry

Massachusetts Maritime AcademyFall 2008

Class Today

• Scavenger Hunt Review• Quiz Answers• Working with Density

The Hunt

• Ok, today we have to learn about density, but you’re going to learn about it on your own for a bit. You’re goal is the answer the following questions. When you are done ask for a quiz. When the quiz is done you are free to leave.

Hunt Objectives

• What is the equation for density.• What is the density of water?• What is the density of mercury metal? Oak

wood? Birch wood? Ethanol? Gasoline? Diesel? Air?

• What happens when you put metal in water? Gasoline in water? Ethanol in water?

• What does the term miscible mean? What does it have to do with the last question?

Also Join Wikispaces

• Go to www.wikispaces.com• Click on get an account• Fill out the form, but don’t get a wiki of your

own.• Check your email• Verify your account• Go to reich-chemistry.wikispaces.com and

click join space.• Confirm with me that it all worked

Quiz 1

• Significant Figures, how many Sig Figs does each of the following numbers have?

• 20,004,000 5• 20,004,000. 8• 000.00043 2• 000.0004300 4• 52,444 5

Quiz 2

• What is a hypothesis? How do experiments relate to hypothesizes?

A theory. Something used to test theory. Good experiments only have 1 variable that are tested.

Quiz Q3

• Convert the following numbers into scientific notation

• 20,004,000 2.0004e7• 20,004,000. 2.004000e7• 000.00043 4.3e-4• 000.0004300 4.300e-4• 52,000 5.2e4

Quiz Q4

• Round the following numbers to the third sig fig.

• 20,004,000 20,000,000• 157.9 158• 000.00043222 0.000432• 000.00043783 0.000438• 52,270 52,300

Quiz Q5

• Add the following numbers, round, and put into scientific notation.

• 5,002 + 3,000 + 1,575 = 1.0e4• 150 + 25 + 88 = 2.6e2• 12,000 + 15,000 + 200,000 2e5• 43.332 - 59.2 - 9.004 -2.49e1• 2.3e3 + 2.55e5+ 5.899e4 3.16e5

Quiz Q6

• Multiply the following numbers, round, and put into scientific notation

• 43.30 * 15.2 / 12 = 5.5e1• 20,202 / 2,000 * 1,525 = 2e4• 241.005 * 15.2 / 150 2.4e1• 0.0042 * 0.00123 * 0.0087 4.5e-7

Quiz Q 7-8

• Convert 1,500 inches into feet. (I don’t care about the number copy the form)

1,500 in * 1ft = 125ft 12 inches• Convert 162 ft into yards. (I want to see the

form!)162 ft * 1 yd = 54.0 yards 3 ft

Quiz Q 9

• Convert 2,220 inches into yards 2220 in * 1 ft * 1yd = 61.6666 => 12 in 3ft

61.7 => 6.17e1

Quiz Q10

• 50,000g into kg50,000g * 1kg = 50kg 1000 g• 4,300 km into m4,300 km * 1,000m = 4,300,000m 1 km

Quiz Q10

• 2.2 L into ml2.2L x 1,000 mL = 2,200mL 1 L • 120 cm into inches120 cm * 1 in = 47.2 2.54 cm

Quiz Q10

• Convert 2,500,542 seconds into years2,500,542 sec * 1 min * 1 hr * 1 day * 1 year = 60 sec 60 min 24 hr 365 days

= 0.079291666666 years= 0.07929167 years= 7.929167e-2

Density

• Density = Mass volume

d = m v

Let’s calculate density

• I have a ball of metal that takes up 3ml and weighs 12.6g. What is it’s density?

d = m v

d= 12.6g= 4.2 g/ml, but 3ml only has 1 sig fig 3mlOK so, finally 4 g/ml would be the answer!

Let’s use density

• In lab I draw out 15ml of a liquid that has 1.67 g/ml. How much mass does it have?

• (copy the given, and use the density)15ml * 1.67 g = 25.05g ml

Let’s use density… Again

• A recipe calls for 200.ml of ethanol, which has a density of 0.789g/ml. How many grams did we add?

200. ml ethanol* 0.789 g ethanol= 157.8 ethanol ml158g => 1.58g e2

Time Left

• OK, we’re going to work on WikisThis only works if you have signed in• 1 open up the web page• 2 click on the atomic history wiki-timeline link• 3 click on your class• 4 click edit this page• Type in:Fall.2008.MMA.lastname1.lastname2.timeline

Making a link

• Highlight the text you just wrote• Click on the icon in the top bar that has a

chain in it.• Click ok when the pop up comes• Click Save• If you do something bad like erase someone

else’s don’t save what you did. Just hit cancel.

Once you make a link

• Click on your link• Hit edit this page• Type in John Dalton looks like D. Reich• Hit Save• Notice how all the computers in the world can

now see that John Dalton looks like D. Reich• You’re going to make your wiki like this.• Be sure to save often!